Sales of Volkswagens have grown steadily at auto dealerships in Nevada during the past $5$ years $($see table below$).$

a$)$ Forecasted sales for year $6$ using the trend projection $($linear regression$)$ method are $626$ sales $($round your response to one decimal place$).$

b$)$ The MAD for a linear regression forecast is sales $($round your response to one decimal place$).$Please solve for the MAD